We had in places 10 of one item like bone armour trait mat but it was 1 piece per slot taking up 10 slots.

So I took every item out of one of my toon bags and dumped the guild bank into it 110 items at a time and stacked anything that could be stacked.

End result was the guild bank went down to 280 of 500.

There was also stuff in there that I sold.

Items sold included...

Stale Radish
Stale Carrots
Foul Hide x 6(which by the way you can only sell, it servers no purpose other then to be sold).
Carapace x 4 (As above)
And a bunch of those level 1-5 bottles of recovery that you find in cabinets which could not be stacked and were taking up way to much space.

Guild bank should really only have the following (in my opinion)

1: Weapons/Armour (so people can see if there is anything they can use either to wear or for crafting research traits if they don't have that trait researched)
2: Quality Food (stale Radish does not meet Guild board of Health standards for quality)
3: Quality Potions (As above, sell the stuff from cabinets to a vender don't put it in the guild bank).
4: Glyphs/Recipes/Food Mats/ Basically stuff other people can use to level their crafting skills.

That's about it. If anyone else can think of more stuff that should be in it, feel free to add it to the list.

Also check what mats are in there before putting yours in.

There are armour trait crafting mats and food crafting mats in there we have 200+ of. We will never go through that.

There is no need to take it to 300,400.500 and taking up more slots with more stacks of 100 of it.

Just sell it to a vendor if you don't want it because in the end if it has to be sold from guild bank to make room again, it probably will have to be.